Paint rollers, also known as paint roller covers, are widely used by both amateurs and professionals to paint surfaces, such as walls and ceilings, quickly and economically, as well as with relative ease. Paint rollers are typically comprised of a tubular core and a paint absorbing cover or layer that is affixed to the core. The tubular core may be a solid structure, or the tubular core may be composed of a helically wound strip or strips of material that are bonded together. The paint absorbing cover may be made from a woven synthetic or natural fabric, or other materials that are well known in the art.
Methods of helically winding strips of materials around a mandrel to form a paint roller are well known. Such methods may allow paint rollers to be manufactured in a continuous, assembly line fashion. Early paint rollers made in this manner used paperboard strips to form the core. In such well known processes, multiple strips of paperboard are helically wound around a mandrel and are bonded together by an application of adhesive between the strips, which cures to form a core. A belt drive is placed on the formed core and is used to advance the core down the assembly line. A second application of adhesive is then applied to the formed core, after which a fabric cover is helically wound onto the formed core. A cutter is then used to cut the endless roller into sticks. The sticks are then cut to size and finished into usable paint rollers.
A disadvantage to paperboard core paint rollers is that paperboard is exceedingly soluble, especially in solvents. As a result, such cores would often times delaminate during use or cleaning.
In an attempt to solve the delaminating problem associated with ordinary paperboard cores, phenolic impregnated paperboard strips were used in lieu of ordinary paperboard. However, even phenolic cores tend to delaminate after prolonged exposure to solvents. In addition, manufacturing processes utilizing phenolic impregnated paperboard strips were slow and required a long assembly line. The use of phenolic impregnated paperboard strips also created environmental issues.
Another attempt to solve the delaminating problem is disclosed in U.S. Pat. No. 5,195,242 issued to Sekar (“the Sekar '242 patent”). In the process described in the Sekar '242 patent, Sekar disclosed helically winding multiple strips of thermoplastic material instead of paperboard or phenolic strips. It is well known that thermoplastic materials are resistant to paint solvents. In particular, multiple strips of thermoplastic material may be helically wound around a stationary mandrel and bonded together using preheated, liquid, thermoplastic to form a core. As with the paperboard and phenolic process, a belt drive is placed on the formed core for advancing the core down the line. A second application of liquid thermoplastic material is then applied to the formed core as an adhesive. A fabric cover is helically wound onto the formed core. A cutter is then utilized to cut the endless roller into sticks. The sticks are then cut to size and finished into usable paint rollers.
The process described in the Sekar '242 patent has several drawbacks. Because the manufacturing process involves the use of multiple strips of thermoplastic material and multiple points of application of liquefied thermoplastic, the process would be difficult to set up and operate. Additionally, such a process is expensive because it requires multiple nozzles for each strip of thermoplastic material. It has also been reported that cores formed of only thermoplastic material tend to be weaker than cores formed of other material, such as metal and cardboard strips; thus the useful life of such paint rollers is relatively short.
U.S. Pat. No. 5,468,207 issued to Bower (“the Bower '207 patent”) disclosed a continuous paint roller manufacturing process using multiple thermoplastic strips similar to the process described in the Sekar '242 patent, with the exception that Bower disclosed using direct heat, instead of liquefied thermoplastic, to bond the thermoplastic strips together to form a core. Bower also disclosed using direct heat, rather than liquefied thermoplastic, to bond the fabric cover to the formed core. The process disclosed in the Bower '207 patent suffers from the same disadvantages as the process disclosed in the Sekar '242 patent. In addition, the use of heaters to bond the multiple thermoplastic strips together and to bond the fabric cover to the formed core is believed to create additional difficulties in the determination of the amount of heat to be applied and the creation of even adhesive layers.
Another well known process that is in present commercial use resolved some of the complexity problems associated with multiple thermoplastic strip processes, such as the processes disclosed in the Bower and Sekar Patents. In this process, which appears to be described in Canadian Pat. No. 2,170,722 also issued to Sekar (“the Canadian '722 patent”), a single strip of thermoplastic material is helically wound about a mandrel, instead of forming a core by helically winding multiple strips. A single application of liquefied thermoplastic material is then applied to the wound strip. Thereafter, a fabric cover strip is helically wound directly over the liquefied thermoplastic and wound strip. A cutter is then utilized to cut the endless formed roller into individual sticks. The sticks are then cut to size and finished into usable paint rollers.
In contrast to certain well known multiple strip processes disclosed in the prior art, such as the Bower and Sekar processes discussed above, a belt drive in the single thermoplastic strip process could not be placed on the wound strip prior to the application of liquefied thermoplastic since there is no formed core prior to the application of the fabric cover. Instead, in the single thermoplastic strip process, the belt drive is placed on the fabric cover so the endless formed paint roller can be advanced down the assembly line.
However, the paint roller resulting from the single thermoplastic strip process described above is prone to certain defects. The ends of the wound strip of such rollers have a tendency to break apart, or unfurl, from the successive wind, which results in the end of the wound strip sticking out, consequently making the roller appear “out of round.” This defect is due to the high tension memory of the thermoplastic strip. In addition, paint rollers made from a single strip of thermoplastic are more susceptible to being crushed and may not have the desirable hardened feel of multiple layer or solid core paint rollers. In an effort to achieve the hardened feel of a multiple layer or solid core paint roller, thicker thermoplastic strips may be used. However, using thicker strips increases the potential for unfurling of the wound strip due to the higher tension memory of the thicker strip.
In view of the complexity of the methods of manufacturing multiple layer paint rollers, such as the phenolic processes in Sekar '242 and Bower '207 discussed above, and further in view of the defects associated with the single strip process described in Sekar's Canadian '722 patent, methods attempting to address one or more of these problems have been disclosed in subsequent patents.
One such method is disclosed in U.S. Pat. No. 6,159,134, also issued to Sekar (“the Sekar '134 patent”). The Sekar '134 patent discloses a method of manufacturing paint rollers comprising the steps of: helically advancing a first strip of thermoplastic material about a mandrel; helically advancing a second strip of thermoplastic material about the first strip of thermoplastic material in offset relation therewith; helically advancing a cover about the second strip; providing an adhesive between the outer surface of the first strip and the inner surface of the second strip; providing an adhesive between the outer surface of the outer strip and the inner surface of the cover; and forming a continuous laminated paint roller by applying a compressive force upon the cover. One disadvantage with this method is that it requires a second strip of thermoplastic material and multiple applications of adhesive. These factors add to production cost and increase the size and complexity of the assembly line. The second strip of thermoplastic material may also increase packaging and bulk transportation costs due to the additional weight of the second strip.
It would therefore be desirable to provide a method for manufacturing a robust, lightweight paint roller utilizing a single strip of base material in the interest of maximizing its structural integrity, decreasing its cost, and decreasing its shipping weight.